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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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VALDEZ AND SHOUP GLACIERS                              249
the valleys to the east. The west wall is consequently oversteepened by glacial erosion up to 1500 feet or more, while on the east side a long rock spur three quarters of a mile south of the glacier was not completely removed, nor the minor rock knobs wholly erased. Even on the eastern side, however, glacial erosion has oversteepened the valley notably, leaving three valleys hanging above the main valley. Corbin Glacier and the one north of it end within their hanging valleys, while the northernmost glacier still cascades out over the lip of its hanging valley. It is not known what the relation is between the Valdez Glacier and Lowe River valley, for their bedrock bottoms are completely buried beneath the outwash gravels; but it is suspected that Valdez Glacier was the master ice tongue and that Lowe River valley, which at present has no glacier, hangs above it.
General Description. The Shoup Glacier,1 at one time called Canyon Creek Glacier, enters Port Valdez just north of Valdez Narrows, terminating a little over two miles back from the main fiord. It has been erroneously represented upon several maps 2 as made up of two glaciers which coalesce two miles from the terminus. As a matter of fact there is no west tributary, but the Shoup Glacier is of a peculiar S-shape CFig. 24). It comes from an unknown source in the Chugach Mountains, perhaps heading on a through glacier pass with the west arm of Valdez Glacier, in a region characterized by Schrader as " a waste of glaciers and nev6." It flows southwest for an unknown distance and then bends sharply southeastward around a right-angled elbow (PI. XCVIH, B) where, 1000 feet above sea level, it is a little over a half mile wide. Below this point it expands to a mile and a quarter and flows to the sea, where its terminus is three quarters of a mile wide. The mountains rise to heights of from 4000 to 6000 feet near the glacier, and the valley walls ascend precipitously from 1000 to 3000 feet. There is an ice cascade at the elbow, below which the glacier slopes smoothly nearly to the water's edge, and there descends steeply again. It descends 1000 feet in the lower five-eighths of a mile, 500 feet of it in the last quarter mile and 200 to 800 feet in the terminal ice fall. The glacier gives an impression of ending on the rock lip of a hanging valley, though its terminus is probably on the face of a step in the main valley bottom. The western half mile of the glacier front ends in the bay, though in very shallow water, while the eastern quarter mile has a delta of outwash gravels and clay in front of it. This delta is an eighth of a mile wide at high tide and three-eighths of a mile at low tide. Across it flows one branching glacial stream from the eastern side of the glacier and a smaller stream from the hanging valley of Canyon Creek, which terminates in a lip a thousand feet above the fiord.
Rock ledges show beneath the glacier at one point behind the delta and at two points in the tidal front (PI. C, A). Near the western edge the basal layers of exposed ice (PI. XCIX) are dirt-laden and simulate rock ledges, though no rock was yet exposed there in 1909. This part of the ice front reaches tidewater, but icebergs are no longer discharged except by tumbling down the precipitous ice front, and the western half of the glacier is apparently just about to cease to be tidal. The water is so shallow that gravel talus cones are formed along the western edge of the ice margin.
i See Chart 8521 and 8519, U. S. Coast and Geod. Survey.
 Maps 20 and 21, Twentieth Ann. Kept., U. S. Geol. Survey, Part VII, 1900; and map accompanying Rept. XXV, War Dept,, Adj.-Gen. Office, 1900.